1. Field of the Invention
The invention relates to a gearbox device, more particularly to a gearbox device having ceramic-incorporating oil seal units.
2. Description of the Related Art
Referring to FIG. 1, a conventional gearbox device includes a tubular housing 1 formed with an axial hole 101 that is defined by first and second hole-confining wall portions 104, 105 opposite to each other along a hole axis of the axial hole 101 and a ring gear portion 103 between the first and second hole-confining wall portions 104, 105, an input shaft 3 mounted rotatably in the first hole-confining wall portion 104, an output shaft 4 mounted rotatably in the second hole-confining wall portion 105, and two oil seals 2, one of which is mounted in the axial hole 101 to provide a liquid tight seal between the input shaft 3 and the first hole-confining wall portion 104, and the other one of which is mounted in the axial hole 101 to provide a liquid tight seal between the output shaft 4 and the second hole-confining wall portion 105. The output shaft 4 has a planet carrier 402 and a set of planet gears 403 mounted on the planet carrier 402. The planet gears 403 mesh with the ring gear portion 103. The input shaft 3 has a sun gear 302 meshing with the set of planet gears 403. The output shaft 4 has a nut 404 mounted thereon for retaining an output bearing in the axial hole 101, the nut 404 being in contact with a corresponding one of the oil seals 2.
The following are some of the drawbacks of the conventional gearbox device:
1. The input shaft 3 and the nut 404 are usually made of alloy steel that has a surface roughness of 0.4 μm. According to an actual test, when the input and output shafts 3, 4 are operated at a speed of 3000 rpm, the oil seals 2, which are made mainly of rubber, wear out after about 20000 hrs as a result of contact with the input shaft 3 and the nut 404. Therefore, the conventional gearbox device is not suitable for applications with a high-speed requirement, such as a printing machine or a weaving machine.
2. Alloy steel has a Vickers hardness of about 450˜600 Hv. As such, after a period of time, the surface roughness of the input shaft 3 and the nut 404 is easily damaged such that the service life of the rubber oil seals 2 is further shortened.